1. Technical Field
The present invention is generally related to a light tracing method and an apparatus, in particular, provided is an optical indexer that determines moving track by incorporating a coherent light interference pattern with a binary imaging method.
2. Description of Related Art
The conventional optical computer mouse is referred to FIG. 1 that depicts inner circuits. This optical mouse 10 moves over a surface 11. Within its device housing 12, the inner circuits include a circuit board 14 in addition to the essential optics elements. Further, a controller 18 used to control, sense and operate light emission, a light source 16, and a sensor 19 are disposed on the circuit board 14.
According to the present example of the optical mouse 10, an aperture 17 directed to external surface 11 is formed on its housing 12. The circuit board 14 is disposed near the aperture 17. A light source 16 such as a laser die or LED is disposed onto the circuit board 14. The light source 16 continuously emits lights to the surface 11 with a specific angle while the optical mouse 10 operates. The shown broken line represents the path of the incident light. A sensor 19 receives reflected light from the surface 11. The sensor 19, such as a CMOS or CCD image sensor, may obtain a distribution diagram made by the reflected light. The controller 18 then obtains a moving direction of the optical mouse 10 by analyzing the energy distribution.
In the conventional technology that determines the moving track of the optical mouse 10, the surface 11 may dominate the performance of tracking the optical mouse 10 since the signals of reflected light made by the surface 11 is the essential information.
For example, the conventional optical mouse 10 may not normally operate when it moves over a transparent material or the surface (11) that hard to reflect the light. Further, the optical mouse 10 may not easily work when it moves over an undulate non-planar surface 11, for example the cloth with wrinkles.
In the conventional technologies, some of them use additional positioning measures to acquire the moving tracks, or some use additional complicated algorithm to maintain a certain ability of tracing the movement. However, theses positioning measures or algorithm may be limited to some types of surfaces because of the limitations of sensitivity, high energy consumption, and complexity. However, these technologies are not applicable to or achieve light tracing over every surface with too high or too low reflectivity.